Method and system for routing a telephone call

BACKGROUND OF THE INVENTION

0001The present disclosure relates generally to the routing of a telephone call from a mobile unit, and particularly to the routing of an emergency telephone call from a cellular phone in signal communication with a cellular telephone system.

0002Cellular telephones include an area code similar to land based telephones referred to as the Number Plan Area (NPA) code, which associates the cellular phone (cellphone) with a particular geographic location. When placing a call to or from a cellphone, the NPA code is used to associate the cellphone with a particular Service Control Point (SCP), which is a processing facility for managing the call connections. A cellphone having a NPA code in a first geographic region but being physically located in a second geographic region will have call features managed by the SCP in the first geographic region, even though the first geographic region may be located at a substantial distance from the actual location of the cellphone in the second geographic region. For a non-emergency cellphone call, this arrangement is appropriate for the purpose of providing cellphone features. However, for an emergency cellphone call it would be advantageous to have a cellular telephone system (CTS) capable of more effectively routing the emergency cellphone call.

0003In a landline emergency 911 (E911) system, an E911 tandem switch routes calls to the proper Public Safety Answering Point (PSAP) based on the Numbering Plan Area Code (NPA-NXX) of the calling number. Once the call arrives at the PSAP, the PSAP can access the Automatic Location Identification (ALI) database to obtain geographic mapping information about the location of the calling number, based on all 10 digits of the calling number.

0004Present Wireless E911 (WE911) system uses one to three “pseudo” phone numbers associated with each cell tower. WE911 calls using this system are routed to the PSAP on the basis of the phone number associated with the cell tower, using the E911 tandem described above. In response, the ALI database retrieves information about the cell site. Since the cell tower possibly uses more than one “pseudo” phone number, this system does not report the accurate location of the caller.

0005While some caller location information is available for wireless callers, improvement in the art is still needed for more effective WE911 call routing.

SUMMARY OF THE INVENTION

0006In one embodiment, a method of routing a telephone call includes receiving the call from a mobile unit in signal communication with a cellular telephone system, and routing the call based at least partially on the geographical location and independent of the number plan area code of the mobile unit.

0007In another embodiment, a method of routing a telephone call includes receiving the call at a mobile switching center from a mobile unit, sending call information to and receiving call information at a service control point that services the geographic area from which the call originated, and providing call routing information based at least partially on the geographical location of the mobile unit.

0008In a further embodiment, a system for routing a telephone call includes a mobile switching center adapted to receive the telephone call from a mobile unit, a signal transfer point in signal communication with the mobile switching center, and a service control point in signal communication with the signal transfer point. The service control point is designated to service a defined geographic area and has a database containing geographic data relating to at least one of the mobile switching center, the service control point, and a public safety answering point in the defined geographic area.

BRIEF DESCRIPTION OF THE DRAWINGS

0009Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying Figures:

0010<figref idref="DRAWINGS">FIG. 1</figref> depicts an exemplary cellular telephone system for implementing an embodiment of the invention;

0011<figref idref="DRAWINGS">FIG. 2</figref> depicts an exemplary communication system in accordance with an embodiment of the invention;

0012<figref idref="DRAWINGS">FIG. 3</figref> depicts an exemplary processing facility referred to as a service control point pair for use in the system of <figref idref="DRAWINGS">FIG. 2</figref>;

0013<figref idref="DRAWINGS">FIG. 4</figref> depicts an exemplary processing facility referred to as a map allocation provisioning system for use in the system of <figref idref="DRAWINGS">FIG. 2</figref>; and

0014<figref idref="DRAWINGS">FIG. 5</figref> is an exemplary method for routing a telephone call in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

0015An embodiment of the present invention provides a method of routing a telephone call, such as a 911 emergency call for example, from a cellphone user, or mobile unit generally, to a local Public Safety Answering Point (PSAP), such as a 911 emergency call center for example, based on geographic information relating to the location of the caller. While embodiments described herein depict an emergency call as an exemplary call from a mobile unit, it will be appreciated that the disclosed invention is also applicable to other telephone calls from mobile units, such as a call requesting operator assistance for example, which would then be routed to an operator who is local to the caller.

0016<figref idref="DRAWINGS">FIG. 1</figref> is an exemplary embodiment of a Cellular Telephone System (CTS) <b>100</b> having a network of cell sites <b>110</b> in signal communication, via data and voice channels (trunk lines) <b>120</b> (not all channels shown) and control paths <b>130</b>, with a Mobile Telecommunications Switching Office (MTSO) <b>140</b> (also referred to as a Mobile Switching Center, MSC). The cell sites <b>110</b> are in signal communication via RF (Radio Frequency) signal <b>150</b> with a mobile unit <b>200</b> held by user <b>170</b>. Mobile unit <b>200</b> may also be operable within an automobile <b>180</b>, or any other transportation means. Each cell site <b>110</b> contains a tower, an antenna, a radio transceiver and a base station controller (collectively <b>110</b>) that manages, sends, and receives traffic to and from a mobile unit <b>200</b> in its geographical area defined by grid <b>190</b> from and to MSC <b>140</b>. MSC <b>140</b> places calls from mobile unit <b>200</b> to land based telephones <b>160</b>, switches calls between cells as mobile units <b>200</b> travel across cell boundaries <b>190</b>, and authenticates the Mobile Identification Number (MIN) of mobile unit <b>200</b>. MSC <b>140</b> is in signal communication with a Local Office (LO) <b>104</b>, which is in signal communication with many MSCs and many land based telephones <b>160</b>. LO <b>104</b> includes a processing center <b>102</b> for processing incoming and outgoing calls.

0017In accordance with an embodiment of the invention, a wireless emergency call, generally referred to as a WE911 call in the United States, is received from mobile unit <b>200</b> at MSC <b>140</b>, sent to LO <b>104</b>, processed at processing center <b>102</b>, and routed to the appropriate PSAP <b>160</b> for the caller <b>170</b> in accordance with an embodiment of the invention. Depending on the shape of the PSAP boundary, the appropriate PSAP <b>160</b> may not necessarily be the closest PSAP <b>160</b>. Numeral <b>160</b> refers to a land based telephone generally and to a PSAP specifically. To accomplish the desired routing of the emergency call to a PSAP <b>160</b> in the local region of the caller <b>170</b>, it is desirable to have the call routed according to information relating to the geographical location of the caller <b>170</b>, as will be discussed in more detail below.

0018Referring now to <figref idref="DRAWINGS">FIG. 2</figref>, which depicts a communication system <b>250</b> for implementing an embodiment of the invention, a user <b>170</b> initiates an emergency (911) call at cell site <b>110</b> from mobile unit <b>200</b>. Upon receipt, the call is handled by MSC <b>140</b> that is in signal communication with cell site <b>110</b>. MSC <b>140</b> may be one of multiple MCSs (i.e., MSC<b>1</b>, MSC<b>2</b>, . . . MSCn) that could have been involved in the call, depending on the geographical location of caller <b>170</b>. Communication of the call signaling information from MSC <b>140</b> is received at a dedicated Service Control Point (SCP) pair <b>310</b> at LO <b>104</b> through Signaling System 7 (SS7) network <b>305</b>.

0019An SCP pair <b>310</b>, depicted in <figref idref="DRAWINGS">FIG. 3</figref>, is an Advanced Intelligent Network (AIN) node that typically includes interconnected computers (processors) <b>312</b> that provide service execution logic, store 911 emergency call data at a database <b>314</b>, and specifically 911 emergency call data relating to wireless communication systems, and store emergency call information at log files <b>316</b>. The SCP pair <b>310</b> is configured as a pair of interconnected Service Control Points, thereby providing system redundancy for enhanced reliability. However, since system redundancy may be accomplished by various means, such as by using three SCPs or by employing redundancy features within a single SCP, for example, SCP <b>310</b>, as used herein, is representative of an SCP pair or any number of SCPs in a reliable configuration. Each SCP <b>310</b> is arranged in signal communication with each of those MSCs that are located in the SCP's defined geographic area of coverage, thereby providing general knowledge to SCP <b>310</b> regarding the general geographic location of mobile unit <b>200</b> depending on which MSC <b>140</b> communicated the call. The efficiency of system <b>250</b> is substantially improved if each SCP <b>310</b>, with its geographic database <b>314</b>, is deployed in a defined geographic area, such as one per state for example, with each location containing the geographic data pertinent to that coverage area.

0020A Map Application Provisioning System (MAPS) <b>320</b>, depicted in <figref idref="DRAWINGS">FIG. 4</figref>, which typical runs on a workstation but may run on any computer system suitable for implementing an embodiment of the invention, is in signal communication with those SCPs <b>310</b> that are part of system <b>250</b>. In an embodiment, MAPS <b>320</b> is arranged as an off-line system, rather than a real-time system, to define PSAP boundaries. Network <b>315</b>, which may be a TCP/IP network or any other network arrangement suitable for implementing an embodiment of the invention, connects SCP <b>310</b> with MAPS <b>320</b>. MAPS <b>320</b> includes a processor <b>322</b> for running the MAPS application software, and Specific Database Engine (SDE) software <b>324</b> for managing database <b>326</b>, which stores, among other data, spatial geographic data for the geographic area of coverage that encompasses MSC <b>140</b>, SCP <b>310</b>, and PSAP <b>160</b>. MAPS <b>320</b> serves as a repository for information defining the boundaries of each PSAP covered by the SCP, and periodically communicates updated information back to the respective SCP <b>310</b> for call processing. Embedded software in an Automatic Location Identification (ALI) database <b>330</b> enables a PSAP user <b>160</b> to query or analyze the results created by relational database <b>326</b> in the form of a geographic map, thereby enabling the visualization of the location of the caller <b>170</b>. Log file <b>316</b> tracks emergency call routing information flowing through SCP <b>310</b>.

0021SCP <b>310</b> receives signaling information related to an emergency call through MSC <b>140</b>, including the geographic location of the caller. Based on the stored geographic boundaries, SCP <b>310</b> determines the correct PSAP <b>160</b> for the caller, which is discussed in more detail below, and then provides information for the MSC to route the emergency call to the appropriate PSAP <b>160</b> and sends location information to an ALI database <b>330</b>, which includes, among other data, information relating to the location of the caller <b>170</b>. In addition to MSC <b>140</b> and SCP <b>310</b>, system <b>250</b> also typically includes a Signal Transfer Point (STP) <b>340</b>, which receives a WE911 query message from MSC <b>140</b> and routes the query to SCP <b>310</b>. Typically, STPs <b>340</b> route messages based on two factors, the type of service, or type of call, the query is providing (referred to as the Translation Type), and the NPA-NXX associated with the query. Depending on the service being provided, this NPA-NXX may be that of the calling number or of the called number. In an embodiment of the invention, additional geographic information is used in conjunction with the Translation Type to route the WE911 message through STP <b>340</b> to the correct SCP <b>310</b> in the geographic region of the caller.

0022In an embodiment, the additional geographic information is provided by a parameter, such as Geographic Location Code (GLC), for example, that is included in the WE911 signaling message by MSC <b>140</b>. This code indicates the state, or other divisional area, in which MSC <b>140</b> is located. STP <b>340</b> is then configured to use the Translation Type and this GLC to determine the routing of the WE911 message.

0023In an alternative embodiment, MSC <b>140</b> includes a “pseudo number” associated with cell site <b>110</b> in the WE911 signaling message. This “pseudo number” is related to the geographic location of cell site <b>110</b>. STP <b>340</b> is then configured to use the Translation Type and the NPA-NXX of the “pseudo number” to determine the routing of the WE911 message.

0024Referring now to <figref idref="DRAWINGS">FIGS. 1</figref>, <b>2</b> and <b>5</b>, embodiments for determining the geographical position of mobile unit <b>200</b>, and caller <b>170</b>, will now be described.

0025In general, and with reference to <figref idref="DRAWINGS">FIG. 5</figref>, which depicts a method <b>400</b> for routing an emergency call, a call is received <b>410</b> at cell site <b>110</b> from mobile unit <b>200</b> and communicated <b>420</b> to MSC <b>140</b>. MSC <b>140</b> routes <b>430</b> the call to SCP <b>310</b> at LO <b>104</b>. Since SCP <b>310</b> is in signal communication with MSC <b>140</b>, as discussed above, the general geographic location of mobile unit <b>200</b> is known. However, in addition to establishing the general geographic location of mobile unit <b>200</b>, a further determination <b>440</b> is made regarding the geographic location of mobile unit <b>200</b>, discussed in detail below. After the geographic location of mobile unit <b>200</b> has been determined, the emergency call is routed <b>450</b> to the PSAP <b>160</b> serving the caller <b>170</b>. At block <b>440</b> of method <b>400</b>, SCP <b>310</b> accesses MAPS <b>320</b> to upload processing data, processes the collective data (call data and uploaded data) to establish the geographical location of the caller and to determine the appropriate PSAP <b>160</b> to the caller, and then routes <b>450</b> the call to that PSAP <b>160</b>.

0026In determining <b>440</b> the general geographic location of mobile unit <b>200</b>, and therefore of caller <b>170</b>, SCP <b>310</b>, after receiving the call from MSC <b>140</b>, accesses MAPS <b>320</b> with information identifying the associated MSC <b>140</b>, and receives in return information from database <b>326</b> correlating MSC <b>140</b> with its geographic location. MAPS <b>320</b> also provides SCP <b>310</b> with information from database <b>326</b> identifying the appropriate PSAP <b>160</b> with respect to the caller <b>170</b>. By having a centralized database <b>326</b> of information, system <b>250</b> can be reconfigured with different associations between MSCs <b>140</b> and SCP <b>310</b> without having to reconfigure every SCP <b>310</b>. A centralized database <b>326</b> also enables system <b>250</b> to be reconfigured with additional or fewer PSAPs <b>160</b> depending on how the demographics of the area change. The information received from MAPS <b>320</b> is uploaded into database <b>314</b> at SCP <b>310</b> and processed at processor <b>312</b>. SCP <b>310</b> also creates an emergency call log file <b>316</b> that may be used by a system administrator for monitoring system <b>250</b> operation. The processed information at SCP <b>310</b> results in the call and associated information being routed to the appropriate PSAP <b>160</b> with respect to mobile unit <b>200</b> and caller <b>170</b>. SCP <b>310</b> also routes call information to ALI database <b>330</b>.

0027An alternative embodiment for determining <b>440</b> a more specific geographic location of mobile unit <b>200</b> includes the use of a Global Positioning System (GPS), which is incorporated into mobile unit <b>200</b>. In response to a call, and specifically to an emergency call, being placed from mobile unit <b>200</b>, a latitude and longitude identifier from the GPS is embedded within the protocol of the call sent by MSC <b>140</b>. This information, along with the known geographic location of MSC <b>140</b> in database <b>314</b>, is passed to SCP <b>310</b> for processing. SCP <b>310</b> accesses MAPS <b>320</b> for geographic data relating to PSAPs <b>160</b>, and then processes the collective data to determine the appropriate PSAP <b>160</b>. SCP <b>310</b> then routes <b>450</b> the call to the appropriate PSAP <b>160</b> and to ALI database <b>330</b>. Alternatively, the longitude and latitude of the caller are dynamically inserted into ALI database <b>330</b>, such that PSAP <b>160</b> can answer and respond to a WE911 call without requiring additional workstation capability.

0028Another alternative embodiment for determining <b>440</b> a more specific geographic location of mobile unit <b>200</b> includes the use of triangulation technology, which is incorporated into the software running on processor <b>312</b> at SCP <b>310</b>. The reception of a call placed from mobile unit <b>200</b> is typically received by more than one cell site <b>110</b>, with the signal strength at each receiving cell site <b>110</b> being determinable. Signal strength information communicated to MSC <b>140</b> is passed to SCP <b>310</b> and used along with data from MAPS <b>320</b>, as discussed above, for determining the appropriate PSAP <b>160</b> to the caller <b>170</b>. SCP <b>310</b> then routes <b>450</b> the call to the appropriate PSAP <b>160</b> and to ALI database <b>330</b>. In an alternative embodiment, signal strength information from cell sites <b>110</b> is used by itself and without triangulation analysis. Here, the geographic location of mobile unit <b>200</b> is based on the cell site <b>110</b> having the strongest call signal strength.

0029As discussed, embodiments of the invention provide PSAP <b>160</b> with information relating to the geographical location of mobile unit <b>200</b>, which may be based on the geographic location of MSC <b>140</b>, or based on signal-related information received at cell sites <b>110</b>. By either method, the geographical location of mobile unit <b>200</b> is determined independent of the number plan area (NPA) code associated with mobile unit <b>200</b>. Accordingly, and in accordance with an embodiment of the invention, a mobile unit <b>200</b> having a NPA code associated with a first geographical region but being in a second geographical region, will have an emergency call originating from the mobile unit <b>200</b> in the second geographical region routed to a PSAP <b>160</b> more appropriate to the mobile unit <b>200</b> in the second geographical region. Additionally, system <b>250</b> of <figref idref="DRAWINGS">FIG. 2</figref> may also include multiple SCPs <b>310</b> for a given geographic region, thereby enabling each SCP <b>310</b> to route a different portion of the data from MAPS <b>320</b>, which would enhance the response time of emergency personnel dispatched from PSAP <b>160</b> to an emergency cellphone call made from mobile unit <b>200</b>.

0030Embodiments of the invention are further exemplified by the following example.

0031Assume there are three wireless callers: Caller-A, Caller-B, and Caller-C. Caller-A is a Georgia resident and the handset number is 404-xxx-xxxx. Caller-B's handset is registered in Louisiana and the number is 318-xxx-xxxx. Caller-C's handset number is 334-xxx-xxxx and it is registered in Alabama. SCP1 contains Georgia subscribers' data. SCP2 has Louisiana subscribers' data. SCP3 contains subscribers' information in Alabama.

0032When Caller-A, Caller-B, and Caller-C make 911 calls in Georgia, existing technology using MSC routes Caller-A's call through STP to SCP1 in Georgia based on Caller-A's NPA (Number Plan Area Code) <b>404</b>, Caller-B's call through STP to SCP2 in Louisiana based on Caller-B's NPA <b>318</b>, and Caller-C's call to SCP3 in Alabama based on Caller-C's NPA <b>334</b>. Hence, while all three calls originated in Georgia, they are routed to different SCPs, based on their registered NPA number, and to different PSAPs.

0033In an embodiment of the invention, which uses geographic location information instead of NPA information, the routing process routes all three calls to SCP1 in Georgia, since the calls were initiated in Georgia. If the calls originated in Louisiana, then the routing process would route the calls to SCP2 in Louisiana. Hence, in accordance with an embodiment of the invention, all three calls are routed to the same PSAP in the caller's state, which is the desired destination.

0034Some embodiments of the invention have the following advantages: the ability to efficiently locate a caller based on the geographical region from where the call was placed; the effective routing of an emergency call to a public safety answering point closest to the caller; the dispatch of emergency personnel from a public safety answering point closest to the caller; improved system efficiency through the use of multiple service control point pairs; effective visualization of the location of the caller using display maps; enhanced system reliability through the use of service control point pairs; the ability to monitor system operations through the use of log files; and, a centralized database for ease in implementing system updates and reconfigurations.

0035While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.